<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>test jq</title>
    <script src="../style/js/jquery-3.4.1.min.js"></script>
</head>
<body>
<div class="aaa"></div>
</body>
<script>
    $('.aaa').addClass('bbb ccc ddd')
    $('.bbb').each((i, tag) => {
        console.log(i)
    });
</script>
</html>